Dynamics of T-Lymphocyte Activation Related to Paradoxical Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome in Persons With Advanced HIV

CD8+ T cell infiltration and proliferation in the brainstem during experimental cerebral malaria

INTRODUCTION

Cerebral malaria (CM) is a lethal neuroinflammatory disease caused by Plasmodium infection. Immune cells and brain parenchyma cells contribute to the pathogenesis of CM. However, a systematic examination of the changes that occur in the brain parenchyma region during CM at the single-cell resolution is still poorly studied.

AIMS

To explore cell composition and CD8+ T cell infiltration, single-cell RNA sequencing (scRNA-seq) was performed on the brainstems of healthy and experimental cerebral malaria (ECM) mice. Then CD8+ T cell infiltration was confirmed by flow cytometry and immunofluorescence assays. Subsequently, the characteristics of the brain-infiltrated CD8+ T cells were analyzed. Finally, the interactions between parenchyma cells and brain-infiltrated CD8+ T cells were studied with an astrocytes-CD8+ T cell cocultured model.

RESULTS

The brainstem is the most severely damaged site during ECM. ScRNA-seq revealed a large number of CD8+ T cells infiltrating into the brainstem in ECM mice. Brain-infiltrated CD8+ T cells were highly activated according to scRNA-seq, immunofluorescence, and flow cytometry assays. Further analysis found a subset of ki-67+ CD8+ T cells that have a higher transcriptional level of genes related to T cell function, activation, and proliferation, suggesting that they were exposed to specific antigens presented by brain parenchyma cells. Brain-infiltrated CD8+ T cells were the only prominent source of IFN-γ in this single-cell analysis. Astrocytes, which have a high interferon response, act as cross-presenting cells to recruit and re-activate brain-infiltrated CD8+ T cells. We also found that brain-infiltrated CD8+ T cells were highly expressed immune checkpoint molecule PD-1, while parenchyma cells showed up-regulation of PD-L1 after infection.

CONCLUSIONS

These findings reveal a novel interaction between brain-infiltrated CD8+ T cells and parenchyma cells in the ECM brainstem, suggesting that the PD-1/PD-L1 signal pathway is a promising adjunctive therapeutic strategy for ECM targeting over-activated CD8+ T cells.

Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome-An Extempore Game of Misfiring with Defense Arsenals

The lethal combination involving TB and HIV, known as "syndemic" diseases, synergistically act upon one another to magnify the disease burden. Individuals on anti-retroviral therapy (ART) are at risk of developing TB-associated immune reconstitution inflammatory syndrome (TB-IRIS). The underlying inflammatory complication includes the rapid restoration of immune responses following ART, eventually leading to exaggerated inflammatory responses to MTB antigens. TB-IRIS continues to be a cause of morbidity and mortality among HIV/TB coinfected patients initiating ART, and although a significant quantum of knowledge has been acquired on the pathogenesis of IRIS, the underlying pathomechanisms and identification of a sensitive and specific diagnostic marker still remain a grey area of investigation. Here, we reviewed the latest research developments into IRIS immunopathogenesis, and outlined the modalities to prevent and manage strategies for better clinical and diagnostic outcomes for IRIS.

Inflammasome genetic variants are associated with tuberculosis, HIV-1 infection, and TB/HIV-immune reconstitution inflammatory syndrome outcomes

Background

Tuberculosis (TB) and AIDS are the leading causes of infectious diseases death worldwide. Here, we investigated the relationship between from single nucleotide polymorphisms (SNPs) of the NLRP3, CARD8, AIM2, CASP-1, IFI16, and IL-1β inflammasome genes, as well as the profiles of secreted proinflammatory cytokines (e.g., IL-1β, IL-18, IL-33, and IL-6) with the TB clinical profiles, TB-HIV coinfection, and IRIS onset.

Methods

The individuals were divided into four groups: TB-HIV group (n=88; 11 of them with IRIS), HIV-1 group (n=20), TB group (n=24) and healthy volunteers (HC) group (n=10), and were followed up at INI/FIOCRUZ and HGNI (Rio de Janeiro/Brazil) from 2006 to 2016. Real-time PCR was used to determine the genotypes of the Single Nucleotide Polymorphism (SNPs), and ELISA was used to measure the plasma cytokine levels. Unconditional logistic regression models were used to perform risk estimations.

Results

A higher risk for extrapulmonary TB was associated with the TT genotype (aOR=6.76; P=0.026) in the NLRP3 rs4612666 Single Nucleotide Polymorphism (SNP) and the C-C-T-G-C haplotype (aOR=4.99; P= 0.017) in the NLRP3 variants. This same Single Nucleotide Polymorphism (SNP) was associated with lower risk against extrapulmonary TB when the carrier allele C (aOR=0.15; P=0.021) was present. Among those with HIV-1 infections, a higher risk for TB onset was associated with the GA genotype (aOR=5.5; P=0.044) in the IL1-β rs1143634 Single Nucleotide Polymorphism (SNP). In contrast, lower risk against TB onset was associated with the A-G haplotype (aOR=0.17; P= 0.026) in the CARD8 variants. Higher IL-6 and IL-33 levels were observed in individuals with TB. A higher risk for IRIS onset was associated with CD8 counts ≤ 500 cells/mm3 (aOR=12.32; P=0.010), the presence of extrapulmonary TB (aOR=6.6; P=0.038), and the CT genotype (aOR=61.06; P=0.026) or carrier allele T (aOR=61.06; P=0.026) in the AIM2 rs2276405 Single Nucleotide Polymorphism (SNP), whereas lower risk against IRIS onset was associated with the AT genotype (aOR=0.02; P=0.033) or carrier allele T (aOR=0.02; P=0.029) in the CARD8 rs2043211 Single Nucleotide Polymorphism (SNP) and the T-G haplotype (aOR=0.07; P= 0.033) in the CARD8 variants. No other significant associations were observed.

Conclusions

Our results depict the involvement of genetic polymorphisms of crucial innate immunity genes and proinflammatory cytokines in the clinical outcomes related to TB-HIV coinfection.

Diagnosis and treatment of tuberculosis in adults with HIV

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), continues to pose a major public health problem and is the leading cause of mortality in people infected with human immunodeficiency virus (HIV). HIV infection greatly increases the risk of developing TB even before CD4+ T-cell counts decrease. Co-infection provides reciprocal advantages to both pathogens and leads to acceleration of both diseases. In HIV-coinfected persons, the diagnosis and treatment of tuberculosis are particularly challenging. Intensifying integration of HIV and tuberculosis control programmes has an impact on reducing diagnostic delays, increasing early case detection, providing prompt treatment onset, and ultimately reducing transmission. In this Review, we describe our current understanding of how these two pathogens interact with each other, new sensitive rapid assays for TB, several new prevention methods, new drugs and regimens.

CD4 T cells are rapidly depleted from tuberculosis granulomas following acute SIV co-infection

HIV/Mycobacterium tuberculosis (Mtb) co-infected individuals have an increased risk of tuberculosis prior to loss of peripheral CD4 T cells, raising the possibility that HIV co-infection leads to CD4 T cell depletion in lung tissue before it is evident in blood. Here, we use rhesus macaques to study the early effects of simian immunodeficiency virus (SIV) co-infection on pulmonary granulomas. Two weeks after SIV inoculation of Mtb-infected macaques, Mtb-specific CD4 T cells are dramatically depleted from granulomas, before CD4 T cell loss in blood, airways, and lymph nodes, or increases in bacterial loads or radiographic evidence of disease. Spatially, CD4 T cells are preferentially depleted from the granuloma core and cuff relative to B cell-rich regions. Moreover, live imaging of granuloma explants show that intralesional CD4 T cell motility is reduced after SIV co-infection. Thus, granuloma CD4 T cells may be decimated before many co-infected individuals experience the first symptoms of acute HIV infection.

Frequency of CXCR3+ CD8+ T-Lymphocyte Subsets in Peripheral Blood Is Associated With the Risk of Paradoxical Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome Development in Advanced HIV Disease

Background

Tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) is a clinical aggravation of TB symptoms observed among a fraction of HIV coinfected patients shortly after the start of antiretroviral therapy (ART). Of note, TB-IRIS is characterized by exacerbated inflammation and tissue damage that occurs in response to the elevated production of CD4+ T cell-derived IFN-γ. Nevertheless, the possible participation of CD8+ T cells in TB-IRIS development remains unclear.

Methods

We performed a comprehensive assessment of the composition of CD8+ T cell memory subsets and their association with circulating inflammation-related molecules in TB-HIV coinfected patients initiating ART.

Results

We found that TB-IRIS individuals display higher frequencies of Antigen-experienced CD8+ T cells during the onset of IRIS and that the levels of these cells positively correlate with baseline mycobacterial smear grade. TB-IRIS individuals exhibited higher frequencies of effector memory and lower percentages of naïve CD8+ T cells than their Non-IRIS counterparts. In both TB-IRIS and Non-IRIS patients, ART commencement was associated with fewer significant correlations among memory CD8+ T cells and cells from other immune compartments. Networks analysis revealed distinct patterns of correlation between each memory subset with inflammatory cytokines suggesting different dynamics of CD8+ T cell memory subsets reconstitution. TB-IRIS patients displayed lower levels of memory cells positive for CXCR3 (a chemokine receptor that plays a role in trafficking activated CD8+ T cells to the tissues) than Non-IRIS individuals before and after ART. Furthermore, we found that CXCR3+ naïve CD8+ T cells were inversely associated with the risk of TB-IRIS development. On the other hand, we noticed that the frequencies of CXCR3+ effector CD8+ T cells were positively associated with the probability of TB-IRIS development.

Conclusion

Our data suggest that TB-IRIS individuals display a distinct profile of memory CD8+ T cell subsets reconstitution after ART initiation. Moreover, our data point to a differential association between the frequencies of CXCR3+ CD8+ T cells and the risk of TB-IRIS development. Collectively, our findings lend insights into the potential role of memory CD8+ T cells in TB-IRIS pathophysiology.